Untitled document.PDF Reproductive Biology

Scrotum An oval sac located outside the body that houses the testes Temperature vs. Sperm Viability Sperm is affected by temperature: optimal temp for sperm production 1-4 C cooler than body temp Testes Primary organs for repro in bulls, responsible for sperm production and production...

Scrotum An oval sac located outside the body that houses the testes Temperature vs. Sperm Viability Sperm is affected by temperature: optimal temp for sperm production 1-4 C cooler than body temp Testes Primary organs for repro in bulls, responsible for sperm production and production of testosterone Testosterone Male sex hormone Production of testosterone Produced in testes, responsible for the development of secondary sex characteristics and maintenance of normal function in the accessory sex glands Cryptorchid Tests fail to descend into scrotum Function of Testosterone Supports the development of secondary sex characteristics and maintains normal function of accessory sex glands in bulls Epididymis A coiled duct leading out of the testes functions of epididymis Absorbs fluid, reduces fluid volume, and stores sperm Secretions of the epididymis Produces substances believed to support sperm viability Vas Deferens Duct that connects the coiled duct leading from the testes to the ampulla Ampulla Shared passage for sperm, made of strong muscular tissue that helps move semen from the duct to the urethra while also adding some fluid Urethra Passage shared by the urinary and reproductive systems Accessory Sex Glands Seminal vesicles, prostate (relatively small in bulls), and Cowper's gland (bulbourethral gland) Function of Accessory Sex Glands - Sperm Survival Secrete fluids that increase the survival potential of sperm Function of Accessory Sex Glands - Sperm Transport Provide a medium to facilitate the movement of sperm Function of Accessory Sex Glands - Sperm Activation Activate sperm, making them motile Function of Accessory Sex Glands - Nutrient Secretion Produce fructose and citric acid, which support sperm energy needs Function of Accessory Sex Glands - Urethra Prepartion Flush the urethra before ejaculation Penis It contains an S-shaped survive that straightens to allow extension for semen release and vaginal insertion Sheath Protective covering that encloses the reproductive organ when in a relaxed state Sheath handling in AI During artificial insemination, the covering is grasped instead of reproductive organ Cryptorchid Fertility Impact Fertility reduced or lost due to testes being too worm for effective sperm production Hormone Production in Cryptorchid Bull Testosterone production is unaffected because Leydig cells are not temperature-sensitive, allowing development of secondary sex characteristics and normal mating behavior. Age of puberty for bulls 6-12 months Age at which bulls can be used regularly for semen collection or breeding 18-20 months Primary functions of female reproductive system Produce female sex cells (eggs or ova), produces steroid hormones and provides a location for a fertilized egg to develop Location of female reproductive organs Housed within the body, positioned below the rectum, which allows for easy access during artificial insemination (AI) Ovary Primary reproductive organ in females, about the size of a walnut Functions of Ovary Produces eggs and female hormones, supports secondary sex characteristics, regulates the estrous cycle, and maintains pregnancy through progesterone Ova Production at Birth At birth, ovaries can produce thousands of ova, though only about 100 are potentially ovulated Ovulation Frequency One egg (ova) is released per estrous cycle Egg Development at Puberty Eggs begin to develop in the cortex (outer portion) of the ovary Follicle A fluid-filled cavity where an egg grows and develops in the ovary. Graafian Follicle The mature follicle that blisters on the surface of the ovary before ovulation. Ovulation The release of a mature egg from the ovary Maintenance of Pregnancy Maintained by progesterone produced by the corpus luteum located in the ovary Oviducts (Fallopian Tubes) Transport eggs to the uterus and serve as the site of fertilization Cervix A physical barrier between the vagina and uterus, which changes during the estrous cycle Cervical Mucus During the Non-heat When the female is not in estrus, the cervix is covered by thick, mucus-like material Cervical Mucus During Estrus During estrus, cervical mucus becomes thin, clear, and stringy Polyestrous A type of estrous cycle where females experience cyclic estrous periods year-round. Examples include cows, sows, rats, and guinea pigs Seasonal Polyestrous A type of estrous cycle where ovulation occurs regularly for part of the year, typically related to day length. Examples includes, mares, ewes, and does Monoestrous A type of estrous cycle with on fertile period per year, seen in many birds (but not all) and whales Proestrus The first stage of the estrous cycle lasting 1 day, leading up to estrus What is estrus? The stage of sexual receptivity in female mammals. How long does estrus last? 12-18 hours. When does ovulation occur in relation to estrus? About 10-12 hours after the onset of estrus. Metestrus The stage of the estrous cycle lasting 7 days, occurring after estrus Diestrus The stage of the estrous cycle lasts 11.5 days, occurring after metestrus Signs of Estrus Include mucus secretion, mounting or riding other cows, standing to be mounted, loss of appetite, decreased milk production, and nervous, excitable behavior. Breeding for AI Timed to match ovulation, typically occurring during estrus. Estrus Vs Estrous Estrus is the period of sexual receptivity. Estrous is the entire productive cycle Methods of heat detection Chalk, temperature indicator, AI Trends in Dairy Cattle Most dairy cows and heifers in the U.S. are bred using artificial insemination. AI Trends in Beef Cattle A much smaller percentage of beef cows and heifers in the U.S. are bred using artificial insemination. AI Use in Dairy vs. Beef Cattle (2014) As of 2014, 80% of dairy cattle were bred by AI, while only 4% of beef cattle were bred by AI. Copulation (Collection Method) A method of semen collection involving natural mating. Vaginal Spoon (Collection Method) A tool used to collect semen, though contamination of the sample may occur. Massage (Collection Method)Used when artificial vagina (AV) or electroejaculation cannot be employed, involving massage of the seminal vesicles and ampulla via the rectum. Electroejaculator A device that applies a mild current across the accessory sex glands to collect semen. Electroejaculator - Advantages No training of the donor bull is required, and it produces good-quality ejaculates. Electroejaculator - Disadvantages May cause muscle tremors, potential injury to the bull, and sometimes result in a spermless ejaculate. Artificial Vagina (AV) A semen collection method that mimics natural conditions by using temperature, texture, and lubrication. AV Preparation The artificial vagina is prepared with warm water (about 110˚F), a flexible rubber inner lining, and a warm water jacket for optimal conditions. AV Lubrication Lubrication is used in the artificial vagina to facilitate semen collection. Artificial Vagina (AV) - Procedure To collect semen, the bull is teased with a false mount or a cow to improve semen quality, and the penis is diverted into the artificial vagina by grasping the sheath. Collection Frequency The bull can be collected 2-3 times per week, with about 1-3 ejaculations per session. AV Collection Limitations Too frequent collections should be avoided to ensure semen quality is maintained. Artificial Vagina - Advantages Feels natural to the bull, is fast, relatively aseptic, and yields excellent quality and quantity of semen. Artificial Vagina - Disadvantages Requires training of bulls, cannot be used with crippled bulls, and may have issues with inexperienced or low libido bulls. Semen Collection - Evaluation During semen collection, volume is measured, and concentration, motility, and morphology are evaluated. The color is checked for creamy yellow, granular, and slightly viscous. Semen Extender An extender is added to dilute and preserve semen, typically containing egg yolk or milk, antibiotics, citric acid, and glycerol. Semen Freezing Semen is packaged in straws and frozen in liquid nitrogen (-300°F), allowing for long-term storage. Average Semen Collection One average semen collection contains enough sperm to breed approximately 300 cows. Enumeration - Concentration Semen concentration can be measured using a hemocytometer, photoelectric colorimeter, or Coulter counter. Motility Motility refers to the ability of sperm to move effectively. Viability - Live/Dead Viability is assessed using dyes like Methylene or Trypan Blue. Live sperm are clear, while dead sperm are blue. Typical viability is 70-85% live. Semen Morphology Around 15% of sperm abnormalities are expected in a typical semen sample. Morphology and Fertility In 25% of collections, fertility is significantly affected by morphologic problems in sperm. Type of morphology AI AdvantagesAllows for wider use of superior sires, higher-quality semen, better disease control, use of injured bulls, and bull proving, while reducing the danger of working around bulls AI Cost heavier fencing and feed, but are outweighed by other advantages like disease control. AI Disadvantages The need to observe heats, careful semen handling, record-keeping for heats and semen inventory, time commitment, and training requirements. Estrus Synchronization Controlling or manipulating the estrous cycle so that females express estrus at the same time. Estrus Synchronization - Uses Useful for artificial insemination (AI) and embryo transfer. Estrus Synchronization - Types Prostaglandin F2α (PGF2α), Gonadotropin-releasing hormone (GnRH), and Progestin-based protocols. Combination Protocols PGF2α - GnRH, Progestin - PGF2α, and GnRH - Progestin. PGF2α Protocol Prostaglandins, like PGF2α, are fatty acids that act as hormones and cause the regression of the corpus luteum. PGF2α Effect on Estrus After administering PGF2α, cows will exhibit estrus 2-5 days later. PGF2α Timing effective only on cows that are between 5-17 days into their estrous cycle. GnRH Protocol GnRH controls the follicular phase of the estrous cycle by stimulating the release of FSH (follicle-stimulating hormone). GnRH and Ovulation If a dominant follicle is present, GnRH injection will cause an LH surge and trigger ovulation. GnRH Effect on Progesterone Overrides the effects of progesterone during the estrous cycle. Follicular Waves 3 follicular waves per estrous cycle. GnRH Timing administered during the follicular phase, when a dominant follicle is present, to induce an LH surge and trigger ovulation. GnRH Protocol Timing Used to synchronize estrus, with timing depending on the specific synchronization protocol being used (e.g., in combination with PGF2α). Progestin Protocol Acts like progesterone, prolonging the luteal phase and preventing ovulation. Progestin Removal Once removed, progesterone levels drop, leading to estrus and ovulation in cows FSH (Follicle-Stimulating Hormone) Stimulates the growth and maturation of ovarian follicles in females and is crucial for initiating the follicular phase of the estrous cycle. LH (Luteinizing Hormone) Triggers ovulation by causing the mature follicle to release an egg, and it also promotes the formation of the corpus luteum, which secretes progesterone to maintain pregnancy. Hormones That Increase at Ovulation Increase in LH (Luteinizing Hormone) and FSH (Follicle-Stimulating Hormone), which trigger the release of the egg from the mature follicle. What hormone prepares the uterus for pregnancy? Progesterone What does progesterone do to the uterine lining? It maintains the uterine lining. What effect does progesterone have on ovulation? It inhibits further ovulation. Where is progesterone produced after ovulation? By the corpus luteum. Age of Puberty for Heifers About 6-9 months Length of gestation About 285 days Average weight of Jersey and Holstein calves Holsteins 80-120 lbs. Jerseys 45-80 lbs. Maternity Pen Timing Placed in a maternity pen 3-5 days before parturition to prepare for calving, although realistically, it is often 1 day, especially when individual maternity pens are not available. Signs of Approaching Parturition Vulva swelling, relaxation of tail head tissue, nervousness, separation from other animals, and muscular exertion. Hooves down is often a reliable indicator for when parturition is near. Navel ill Navel infection in newborn calves, kids, lambs, and foals Symptoms of Navel Ill Loss of appetite, swollen and sore joints, umbilical swelling, and discharge Prognosis of Navel Ill Poor if left untreated, as the infection can spread and worsen Causes of Navel Ill Bacteria such as E. Coli, Streptococci and Pasteurella, which infect the umbilical cord of newborn animals Purpose of Navel Dipping at Birth Prevents infection organisms from entering the umbilical cord, reducing the risk of navel ill in newborn calves, kids, lambs, and foals Common Navel Dips Used 2-7% iodine tincture, Chlorhexidine, and Navel Guard Failure of Passive Transfer 40% of suckling calves fail to receive enough antibodies, raising disease risk Disease risk from suckling Calves may ingest bacteria from dirty teats, risking infection Importance of sanitizing teatsSanitizing teats reduces calf exposure to pathogens and disease Suckling vs. bottle feeding Bottle feeding ensures proper colostrum intake, reducing FPT risk. Passive Immunity in Calves Calves rely on colostrum for antibodies; FPT occurs if intake is inadequate. Newborn Calf Immune StatusNo adaptive immune response at birth; innate response still developing. Importance of Colostrum Provides vitamins, immunoglobulins (lg), and maternal leukocytes Immunoglobulin G (IgG) Most important Ig in blood and tissues; key for passive immunity in calves Cortisol effect at birth High cortisol suppresses immune response for 7 days post-birth Maternal antibody half-life Lasts 16-28 days; maternal interference can persist up to 6 months. Oral Vaccines for calves Must be given before colostrum or risk being inactivated Intranasal (IN) vaccines Avoid maternal antibody interference but have shorter immunity duration Vaccination Timing (SC/IM) Subcutaneous (SC) or intramuscular (IM) vaccines given at 4-6 months Oral Vaccine at Birth Rotavirus and coronavirus oral vaccine given 30+ min before colostrum Vaccination Delay IBR, BVD, PI-3, BRSV, and leptospirosis vaccines delayed 3-6 months if injected Scours Diarrhea in calves caused by infection, poor nutrition, or digestive issues. Causes of Scours Infections (E. coli, Clostridia), excess undigested protein, excess carbohydrates, or poor feeding practices. Putrefactive Scours Caused by undigested protein, leading to bacterial fermentation, intestinal damage, and diarrhea. Prevention of Putrefactive Scours Monitor non-casein levels in milk replacer to reduce undigested protein. Fermentative Scours Caused by excess carbohydrates, leading to fermentation, increased osmotic pressure, and diarrhea. Indicator of Fermentative Scours Low pH in feces due to volatile fatty acids (VFAs) and lactic acid. Prevention of Fermentative Scours Avoid overfeeding carbohydrates; prefer lipids since they do not ferment. Negatives of Allowing Calf to Suckle from Dirty Teat Increases risk of bacterial pathogen transfer from cow to calf, impairing antibody absorption and reducing Ig receptor availability. Bacterial Impact on Ig Absorption Bacteria from dirty teats can impair antibody (Ig) absorption, reducing immune protection in calves. Failure of Passive Transfer (FPT) Rate from Suckling Calves allowed to suckle have a 40-60% risk of Failure of Passive Transfer (FPT) due to unknown colostrum intake and quality. Suckling Method Disadvantages Uncertainty in colostrum quantity, quality, timing of intake, and bacterial quality, all of which impact calf immunity. Best Colostrum Feeding Method Hand-feeding colostrum with a bottle or esophageal feeder ensures controlled intake of quantity, quality, and timing. Key Components Higher in Colostrum than Milk Immunoglobulins, carotenoids, fat-soluble vitamins, minerals, and protein are higher in colostrum than in milk. Immunoglobulin Concentration in Colostrum Colostrum contains 55-68 g/kg of immunoglobulins, essential for newborn pathogen defense. Lactose in Colostrum vs. MilkColostrum has lower lactose compared to milk, matching the newborn's low lactase activity at birth. Why Newborns Absorb Ig from Colostrum Newborns absorb immunoglobulins due to low intestinal proteolytic activity and a permeable intestinal epithelium during the first 24 hours. Colostrum Production Relative to Calf Needs Cows produce twice the amount of colostrum needed by the calf, allowing for freezing and later use. When should calves receive colostrum after birth? Within 30-60 minutes of birth if ideal. Best before 6 hours. Ig decreases if you wait too long How much colostrum should a Holstein calf receive within the first hour? 1 gallon. How much colostrum should calves receive again after the first dose? 2 quarts. What percentage of body weight should calves receive in colostrum within the first hour? 10% of body weight. Key Quality Factors of Colostrum Should be free of blood, debris, and mastitis, come from a healthy vaccinated cow, have bacteria counts 50 g/L IgG. Good quality Ig 20-30% on brix refractometer, 50-80 g/l What is the effect of high-quality colostrum on calf immunity? High-quality colostrum improves calf immunity. How does high-quality colostrum affect the risk of disease in calves? It reduces the risk of disease. What are the benefits of high-quality colostrum for calf growth and survival? It supports better growth and survival rates. What factors determine the quality of colostrum? IgG concentration, Brix %, and cleanliness. Factors Affecting Colostrum IgG Concentration : Colostrum from older cows and colostrum produced in warmer temperatures (>21°C or 71°F) has higher IgG concentration. How long can colostrum be stored in a refrigerator? Up to 7 days before IgG concentration declines. What is the recommended method for thawing frozen colostrum? Thaw in warm water or at room temperature, not hot water. Whey Protein Denaturation Occurs above 60°C, affecting immunoglobulins (Ig). Casein Protein Denaturation Occurs at 145°C, much higher than pasteurization temps. Pasteurization Temp & Time 63°C for 30 min or 72°C for 15 sec to kill bacteria. How does heat-treating colostrum affect bacterial load? Reduces bacterial load and lowers total plate count. How does heat-treating colostrum affect IgG concentration? Slightly reduces IgG concentration in colostrum. How does heat-treating colostrum affect serum IgG in calves? Increases serum IgG in calves, improving passive transfer. How does heat-treating colostrum affect serum total protein in calves? Increases serum total protein in calves. At what temperature do whey proteins denature? 65°C (149°F). Does pasteurization at 63°C for 30 min denature whey proteins? No, it stays below the 65°C denaturation threshold. Does heat-treating affect casein proteins in colostrum? No, casein proteins denature at 145°C, much higher than pasteurization temperatures. Esophageal Feeder A device used to deliver colostrum or milk directly into the esophagus of a calf, bypassing the mouth and depositing the liquid into the reticulo-rumen. Outflow into the abomasum occurs within 3 hours. Pros of Esophageal Feeder efficient feeds, saves time, consistency Cons of Esophageal Feeder Lowers IgG absorption compared to bottle feeding, delayed absorption, potential for misuse Esophageal Groove Tissue lips directing milk to the abomasum, preventing it from entering the rumen. Groove Closure - Longitudinal Muscle Contraction shortens the groove, transferring 40% of milk. Groove Closure - Right Lip Inversion Inversion forms a tube, transferring 90% of milk to the abomasum. ScourGuard 4KC A vaccine for pregnant cows and heifers to prevent calf diarrhea caused by rotavirus, coronavirus, E. coli, and Clostridium perfringens. ScourGuard 4KC Components Contains inactivated rotavirus, coronavirus, K99 E. coli bacterin, and Clostridium perfringens type C toxoid. ScourGuard 4KC Vaccine Mechanism Stimulates immune response to protect calves from multiple pathogens causing scours. Ear tags Metal or plastic tags punched through the ear cartilage for calf identification. Tattoos (for Identification) Dye injected into the skin, usually applied to the ear for calf identification. Branding Freeze or hot branding used for calf identification, more common in commercial herds. Photos and Drawings Visual records used as part of routine identification for registered cattle. Registration Certificate Document including calf's name, sex, birthdate, sire, and dam for identification Electric (Hot) Iron Dehorning Most common dehorning method, done at less than 8 weeks, takes 20-30 seconds per horn bud, bloodless, less infection, and avoids disfiguring the poll. Chemical Pastes (Dehorning)Caustic paste applied to the horn base to chemically burn the horn tissue, generally bloodless, but can cause tissue burns if transferred. Barnes Dehorner Quick dehorning method for older calves, can be bloody, may leave scars, and has a higher risk of infection. Tube Scoop Rare dehorning method that gouges out horn tissue, typically bloody with a higher risk of infection. What is the first step in cleaning calf feeding utensils? Rinse with lukewarm water (100°F/38°C). What temperature should the soap and hot water be when washing calf feeding utensils? 170°F/77°C. What should you use to rinse calf feeding utensils after washing with soap? Chlorine and cold water. What cleaning agents should be used for calf feeding utensils? Soap and chlorine washes or acid rinses. Why Use Cold Water for Chlorine Wash? Chlorine (bleach) contains sodium hypochlorite, which is inactivated by hot water, reducing its effectiveness. Acid Wash for Feeding Utensils An alternative to chlorine wash, often followed by drying to prevent bacterial growth (as bacteria need water to grow). Which type of feeding utensils is more common? Plastic Why are plastic feeding utensils easier to clean than metal? Due to lower corrosion risks and ease of handling What does Calf Starter mainly consist of? Concentrates rather than roughage Why are concentrates important in Calf Starter? They aid in the production of butyrate, a key fatty acid for rumen growth. When to Start Calf Starter around 1 week of age, with some managers rubbing starter in the calf's mouth to encourage consumption. Importance of calf starter Helps with rumen development, especially the production of butyrate, essential for healthy rumen growth. How much calf starter should calves consume by 5-6 weeks of age? Over 1.5 lb/day When should weaning occur if calf starter intake is sufficient? At 5 to 6 weeks of age Is it acceptable to wean calves at 8-12 weeks? Yes, if intake is not an issue Socializing Calves Before Weaning Socialize calves prior to grouping during weaning to reduce stress and promote healthy group dynamics. Calf Starter Feeding Timing Start offering calf starter at approximately 1 week of age. Average age for starter feeding is 8.5 days. Initially, provide small amounts. Calf Starter Nutrients Calf starter should be 18-22% protein, 3% fat, 50-60% NFC, 82% TDN, and 12-14% NDF, to support rumen development. Importance of Fresh Calf Starter Always provide clean, fresh starter to prevent off-flavors, dust, and mold, and support healthy calf growth. Rumen Development and Concentrate Feeding High concentrate feeding supports rumen development due to butyrate and propionate production, whereas forage fermentation produces less beneficial acetic acid. Calf Starter Texture Calf starter can be fed as mash or pellets. Pelleted starter may be easier for calves to consume. Water for Calves Clean, fresh water should always be available. Proper water management can prevent scours, and calves need extra water in hot conditions. Weaning Timing Weaning occurs when calves are eating at least 1.7 lb of starter per day for 3 consecutive days. Feeding from 3-10 Months Shift from calf starter to a concentrate mix. Aim for 3-4 lb of concentrate/day for growth without fattening. Feeding from 10 Months to Pre-Calving Heifers need adequate roughage and possibly some concentrate to reach proper size (750-800 lbs) for breeding at 14-17 months. Pre-Calving Nutrition Close-up dry cow diets with concentrate may be fed in the last 2-3 weeks before calving to meet nutritional needs. Heifer Replacement Program Goal Aiming for low calf mortality (